This invention relates to push-push oscillator circuits constructed in microstrip or stripline form and, more particularly, to a push-push microwave oscillator circuit having two active branches stabilized by a common ring resonator of superconducting material.
Push-push microwave oscillators are constructed of two active branches, each of which comprises an active element and transmission line sections, plus some form of resonator which locks the oscillations of the two branches to produce a stable output signal. One such circuit, disclosed in Pavio, Jr. et al., U. S. Pat. No. 4,763,084, employs a circular disk of dielectric material to serve as a common resonator for the two branches. Dielectric resonator stabilized oscillators (DRO's) are described also in an article entitled "DRO State of the Art" by Chen Y. Ho et al., appearing in the journal APPLIED MICROWAVE, Spring 1990, Pages 69-80. The dielectric resonator is constructed of a ceramic material which is specially prepared for use at the microwave frequencies, and is subsequently inserted into the oscillator circuit and precisely positioned near a transmission line to provide a desired amount of coupling for stabilizing the oscillator frequency.
A problem arises in that the foregoing type of oscillator circuitry does not provide as high a frequency stability as may be desired for certain signal processing applications such as for satellite communication systems. A further problem arises because the foregoing type of resonator must be fabricated separately from the oscillator circuit, and has a thickness which is larger than that of components of a stripline or microstrip circuit, both of these considerations militating against automated manufacture of the oscillator circuit in large quantities.